1. Field of the Invention
The present invention relates to a monitor, and more particularly, to a brightness correcting circuit for correcting the brightness of a monitor screen and a brightness correcting method using the same.
2. Description of the Related Art
To produce an image on a monitor screen, a video signal is scanned to the screen via an electron gun. The video signal indicates a "black level" constant direct current (DC) voltage which controls the brightness of the screen. Since different users generally desire different brightnesses of the screen, monitors are constructed so that a user can change the brightness of the screen. As the size of a monitor screen becomes larger, the surface of the screen becomes generally non-spherical, i.e., it approaches a curved surface close to a planar surface.
As an example, a schematic diagram of a picture tube is shown in FIG. 1. Referring to FIG. 1, an electron gun 110 creates an electron beam using a video signal Vout as an input and reproduces an image on a screen 130 by controlling the intensity of the electron beam. When the screen 130 is non-spherical, a distance from the electron gun 110 to the screen 130 is not uniform. Namely, a distance 11 or 13 from the electron gun 110 to the edge of the screen 130 is greater than the distance 12 from the electron gun 110 to the center of the screen 130.
Accordingly, in a conventional monitor, the brightness at the edge of the screen 130 is generally lower than that at the center. In particular, the brightness is most greatly reduced in the comers of the screen.